Cardiac functional studies were made and endomyocardial biopsies were obtained on 24 patients who received epirubicin in total cumulative doses arranging from 180 mg/m(2) to 918 mg/m(2) for the treatment of neoplasm. A total of 20 biopsies were evaluable. Histologic and ultrastructural changes were similar to those caused by other anthracycline agents. A strong correlation was demonstrated between total dose of epirubicin and pathologic change as quantified using the Billingham scale (r = 0.7, p = 0.0006). Patients who are expected to receive epirubicin in excess of 450 mg/m(2) should be based on the results of monitoring.